The synthesis and characterization of a new PEDOT-carbon composite prepared using a microporous carbon template are described. The electrochemical behavior of this composite, as well as that of three other colloidal materials-PEDOT-silica, PEDOT, and microporous carbon particles-is investigated with respect to their suitability as electrode materials in supercapacicors. This was accomplished by a combination of cyclic voltammetry and galvanostatic charge/discharge cycles, It was found that the PEDOT-silica composite had the lowest specific capacitance of the four materials (ca. 60 F g(-1)) and also the worst retention of the capacitance at high scan rates. In the case of pure PEDOT, microporous carbon, or PEDOT-carbon microspheres, the specific capacitances of the materials were dramatically higher (C(M) = 115, 109, and 106 F g(-1), respectively). These values are higher than those of either unstructured electropolymerized PEDOT or commercially available high-surface-area carbon. The pure PEDOT materials retained this high capacitive behavior even at faster scan rates, although the capacitance of the carbon and PEDOT-carbon microspheres dropped substantially. These results are interpreted in the context of the local microstructure of the individual colloidal particles, as well as the overall film morphology. The morphologies of both the individual particles and the electrode films were investigated by field-emission scanning electron microscopy. Due to the monodisperse nature of the microspheres, films composed of these materials necessarily possess an interconnected network of interstitial pores that allow for facile ionic diffusion. This allows for more penetration of the conjugated polymer by the ionic electrolyte and therefore higher capacitances relative to the bulk materials. These results demonstrate the feasibility of utilizing monodisperse colloidal microparticles containing conjugated polymers as electrode materials for high-energy and high-power-density supercapacitors.